The goal of this grant is to further develop the novel recombinant vector, Newcastle disease virus (NDV), so that it can be used as a platform to vaccinate humans against bioterrism agents and emerging infectious diseases. An advantage of this strategy is that vaccines for emerging diseases can be quickly made by inserting a protein of the pathogen into the NDV genome. For this grant we will focus on developing vaccines to three dangerous pathogens: potential pandemic influenza virus, Nipah virus, and Chikungunya virus. We will test several different strategies to improve rNDV vaccines. Though NDV has already been safely administered to humans, we will develop single-cycle vaccines that do not spread beyond the initially infected cells. Since these vaccines cannot spread throughout the host, they could be administered safely to immunocompromised individuals. We will develop bi- and triple-segmented rNDV vaccines that are able to express two or three foreign proteins. These viruses will induce a broader immune response compared to recombinant vaccines expressing just one protein of a foreign pathogen. We will also identify the NDV RNA packaging signals and incorporate these signals into the multiple-segmented rNDV vaccines to increase the efficiency of packaging multiple segments into the same virion. One problem with vaccine development is that vaccines are often not very effective in the aged population and strategies are needed to enhance vaccine protection in this group. We will determine whether an adjuvant that stimulates NKT cells, alpha-C-galactosylceramide, can enhance the immunogenicity of the NDV vaccines in both young and aged mice. Another strategy to enhance immunogenicity to rNDV vaccines includes re-targeting the rNDV vaccines to dendritic cells, which is the site of the initiation of the adaptive immune response. This will be accomplished by expressing a single-chain antibody to dendritic cell receptor, DEC-205, from the rNDV genome. We will collaborate with NBC investigator Dr. John Rose to determine whether prime-boost regimens involving vaccinating mice with rNDV expressing influenza virus HA protein and boosting with rVSV expressing influenza virus HA protein can enhance the immune response to influenza virus HA better than either vector alone. To determine whether the vaccines are protective, we will challenge mice with influenza H5N1 at Mount Sinai and collaborate with other RCE investigators to challenge animals vaccinated with Nipah and Chikungunya rNDV vaccines.